Position Determination System and Position Determination Method

1. A position determination system comprising: communication units that are arranged on a communication subject and perform wireless communication with a terminal; and a position determination unit that is arranged on the communication subject and obtains received signal strength indicator data of radio waves transmitted on different frequencies between the terminal and each of the communication units to determine a position of the terminal relative to the communication subject from the obtained received signal strength indicator data, wherein the received signal strength indicator data is obtained for each of the communication units and indicates a received signal strength indicator of each of the radio waves measured for each of the frequencies, one of the communication units is arranged on the communication subject in one of two divided sections obtained by dividing the communication subject along a reference line extending across the communication subject, and another one of the communication units is arranged on the communication subject in the other one of the two divided sections, the communication units include a first communication unit located in one of the two divided sections and a second communication unit located in the other one of the two divided sections, the position determination unit determines the position of the terminal by checking whether first received signal strength indicator data of radio waves transmitted from the first communication unit is approximate to second received signal strength indicator data of radio waves transmitted from the second communication unit, and the position determination unit compares the received signal strength indicator of the radio waves transmitted from the first communication unit and the received signal strength indicator of the radio waves transmitted from the second communication unit for each of the frequencies and determines that the first received signal strength indicator data and the second received signal strength indicator data are approximate when a difference in the received signal strength indicator for each of the frequencies is less than or equal to a predetermined threshold value.

2. The position determination system according to claim 1 , wherein the communication subject includes an interior area that is separated from an exterior area, and the communication units are arranged on the communication subject in the exterior area.

3. The position determination system according to claim 1 , wherein the communication units are arranged in symmetry with respect to the reference line that divides the communication subject.

4. The position determination system according to claim 1 , wherein the communication subject includes a transmissive portion that transmits the radio waves and a non-transmissive portion that does not transmit the radio waves, and the communication units are arranged on the non-transmissive portion of the communication subject.

5. The position determination system according to claim 1 , wherein the communication subject is a vehicle, and one of the communication units is arranged in one of the two divided sections located in a left side of the vehicle and another one of the communication units is arranged in the other one of the two divided sections located in a right side of the vehicle.

6. A method for determining a position of a terminal, the method comprising: transmitting radio waves on different frequencies between the terminal and each of communication units arranged on a communication subject; obtaining received signal strength indicator data of the radio waves; and determining a position of the terminal relative to the communication subject from the obtained received signal strength indicator data, wherein the received signal strength indicator data is obtained for each of the communication units and indicates a received signal strength indicator of each of the radio waves measured for each of the frequencies, one of the communication units is arranged on the communication subject in one of two divided sections obtained by dividing the communication subject along a reference line extending across the communication subject, and another one of the communication units is arranged on the communication subject in the other one of the two divided sections, the communication units include a first communication unit located in one of the two divided sections and a second communication unit located in the other one of the two divided sections, the determining a position of the terminal includes determining the position of the terminal by checking whether first received signal strength indicator data of radio waves transmitted from the first communication unit is approximate to second received signal strength indicator data of radio waves transmitted from the second communication unit, and the checking includes comparing the received signal strength indicator of the radio waves transmitted from the first communication unit and the received signal strength indicator of the radio waves transmitted from the second communication unit for each of the frequencies, and determining that the first received signal strength indicator data and the second received signal strength indicator data are approximate when a difference in the received signal strength indicator for each of the frequencies is less than or equal to a predetermined threshold value.